After color development, silver halide color photographic material is subjected to a desilvering step. Recently, to shorten the delivery time of finished products and decrease laboratory work, it has been desired to shorten the processing time for color photographic materials and, in this case, shortening of the desilvering step is particularly important.
To shorten the desilvering step, the act has investigated shortening not only the two bath type bleaching and fixing steps but also the monobath type blixing (bleach-fixing) step and further the combination of a fixing step and a blixing step or a bleaching step and blixing step. These techniques are generally called bleaching acceleration techniques and fixing acceleration techniques but investigations on the former technique have been a major focus in the art. In particular, investigations have been made on bleaching accelerators.
Practical examples of these bleaching accelerators are compounds having a mercapto group or a disulfide group as described in U.S. Pat. No. 3,893,858, West German Patents 1,290,812 and 2,059,988, Japanese Patent Applications (OPI) 32736/78, 57831/78, 37418/78, 65732/78, 72623/78, 95630/78, 95631/78, 104232/78, 124424/78, 141623/78, and 28426/78 (the term "OPI" as used herein means an "unexamined published Japanese Patent application"), Research Disclosure, RD No. 17129 (July, 1978), etc.; thiazoline derivatives as described in Japanese Patent Application (OPI) No. 140129/75; thiourea derivatives as described in Japanese Patent Publication 8506/70, Japanese Patent Applications (OPI) 20832/77 and 32735/78, U.S. Pat. No. 3,706,516, etc.; iodides as described in West German Patent No. 1,127,715 Japanese Patent Application (OPI) 16235/83; polyethylene oxides as described in West German Patent Nos. 966,410 and 2,748,430; polyamine compounds as described in Japanese Patent Publication 8836/70; and other compounds as described in Japanese Patent Applications(OPI) 42434/74, 59644/74, 94927/78, 35727/79, 26506/80, and 163940/83.
Compounds having a high accelerating effect are rather rare among the aforesaid compounds and, in particular, compounds having a mercapto group or a disulfide group are preferred from the view point of showing a high accelerating effect and, particularly, the compounds described in U.S. Pat. No. 3,893,858, West German Patent No. 1,290,812, and Japanese Patent Application (OPI) 95630/78 are preferred.
However, since these compounds have the disadvantages that they are liable to be air oxidized and further are liable to cause poor fixing, techniques using these compounds are not yet satisfactory.
Techniques using iron (III) complexes of various aminopolycarboxylic acids having a molecular weight of 300 or more as bleaching agents to accelerate bleaching are described in Research Disclosure, RD No. 24023, (April, 1984), Japanese Patent Applications (OPI) 5335/74, 67657/75, 149358/84, 47959/86, 50146/86, 50147/86, etc.
However, when such an iron(III) complex of an aminopolycarboxylic acid having a molecular weight of 300 or more is used as a bleaching agent, the bleaching rate is increased similar to using a bleaching agent having a molecular weight of less than 300, but the effect is still insufficient.
An object of this invention is, therefore, to provide a processing technique for silver halide color photographic materials where the desilvering time is greatly shortened.